Now comes a new rallying cry: software wants to be free. Or, as the tech insiders say, it wants to be “zero dollar.”

A growing number of consumers are paying just that — nothing. This is the Internet’s latest phase: people using freely distributed applications, from e-mail and word processing programs to spreadsheets, games and financial management tools. They run on distant, massive and shared data centers, and users of the services pay with their attention to ads, not cash.

While such services have been emerging for years, their rapid adoption has been an important but largely overlooked driver of the $44.6 billion hostile bid that Microsoft made to take over Yahoo this week.